This invention relates to a method and apparatus for controlled, rapid load transference between first and second support surfaces. More particularly, the present invention relates to transferring a load such as a prefabricated deck from a barge to an offshore deck support structure utilizing improved hydraulic jacks.
It has been found cost effective to fabricate certain major subassemblies of offshore drilling platforms onshore and then join the subassemblies by floating mating operations offshore. The drilling platform deck is one such major subassembly appropriate for onshore fabrication, provided that it can be effectively transferred to deck support structures offshore. Numerous deck support structures might accept such a prefabricated deck including rigid towers, compliant pile towers, semisubmersible vessels, and tension leg platforms.
Prefabricated decks have been joined to deck support structures offshore in the prior art by transporting the deck to the platform site by barge, maneuvering the barge between a plurality of deck support members to position the deck over the deck support members and transferring the weight of the deck to the deck support members by ballasting the barge. Alternatively, hydraulic jacks have been used in the prior art to effect this transfer. However, neither approach has been effective in transferring the deck weight quickly enough to prevent wave motions operating on the barge from slamming both the barge and the deck support members into the deck during the latter stages of load transfer. Further, excessively rapid transfer accentuates the slamming action in that removing the load from the barge too quickly causes excited motions of the floating barge to combine with wave motions of the ambient sea conditions. This problem is even more severe where the deck support structure is itself a floating structure as in the case of semisubmersibles and tension leg platforms.